In 1908, Carl Eigenmann completed a remarkable survey of the fishes of Guyana (Eigenmann, 1912). Included in the survey were parts of the Potaro River drainage above Kaiteur Falls, the largest single-drop waterfall in the world. Until recently, no other ichthyologists had collected above Kaiteur Falls, and several species described by Eigenmann had been known only from the types. In 1998, a team consisting of researchers from the Illinois Natural History Survey, Auburn University, and the University of Guyana, along with a photographer and writer from National Geographic magazine, repeated much of Eigenmanns journey and surveyed the Potaro River and some of its tributaries above Kaiteur Falls.

Among the recent collections are
specimens representing two species of the loricariid catfish genus Corymbophanes.
Eigenmann (1909, 1912) described Corymbophanes andersoni as a new
genus and species based on a single individual from Aruataima Falls, a
cataract on the Potaro River above Kaiteur Falls that has since been renamed
Chenapou Falls (Fig. 1). Corymbophanes is nearly unique among
loricariids in the replacement of the adipose fin by a series of raised,
median, unpaired plates between the dorsal and caudal fins, hereafter referred
to as a postdorsal ridge. Currently, C. andersoni is the only
species recognized in Corymbophanes; however, Chaetostoma venezuelae
(Schultz) and Hemipsilichthys bahianus (Gosline) were originally
described in Corymbophanes (Isbrücker, 1980; Armbruster, 1997).

In the 1998 survey, we collected
additional specimens of Corymbophanes andersoni from the type locality.
We also collected specimens of an undescribed species of Corymbophanes
in Oung Creek, a small tributary of the Chenapou River that empties into
the Potaro River across from the village of Chenapou (Fig. 1). The
information above and the description below is from Armbruster et al. (2000).
Links above are to descriptions of the two known species of Corymbophanes.SPECIES

C. andersoni Eigenmann, 1909

C. kaiei Armbruster and Sabaj 2000.

DIAGNOSIS

Based on Armbruster (1997), characteristics considered
to be synapomorphies for Corymbophanes are the bladelike ventral
surface of the first epibranchial, an elongate anterior process on the
fourth epibranchial, preoperculo-hyomandibula ridge deflected beyond the
posterior margin of the hyomandibula such that it is visible when the suspensorium
is viewed mesially, a spoon-shaped anterior process of the metapterygoid,
bony contact of the canal plate with the suspensorium, the suprapreopercle
absent, a postdorsal ridge present, loss of the adipose-fin membrane and
spine, and loss of the dorsal flap of the iris. All of these characteristics
are found elsewhere in Loricariidae, but they appear to have been uniquely
derived in Corymbophanes based on Armbruster (1997).DESCRIPTION

Corymbophanes can be identified from all
other loricariids by a combination of a postdorsal ridge, lack of an adipose-fin
membrane, lack of the dorsal flap of the iris of the eye, lack of evertible
cheek plates, lack of hypertrophied cheek odontodes, loss of the suprapreopercle,
and three rows of plates on the caudal peduncle. Among loricariids,
the only species with a postdorsal ridge and no adipose-fin membrane are
species of Leptoancistrus Meek and Hildebrand and some
Chaetostoma.
Leptoancistrus
and the Chaetostoma can be separated from
Corymbophanes by
the presence of evertible cheek plates and hypertrophied odontodes, presence
of a dorsal flap of the iris, five rows of plates on the caudal peduncle,
and the loss of the anal fin. Some species of
Hemipsilichthys
also have a large number of median, unpaired, postdorsal plates, but the
plates do not form a ridge. Delturus and Upsilodus
have a postdorsal ridge, but an adipose-fin membrane is present.ECOLOGY

Found in swift riffles.
DISTRIBUTION

Known only from the Potaro River and tributaries above Kaiteur Falls.
Red star = C. andersoni, Blue circle = Corymbophaneskaiei,
1 = the village of Chenapou, 2 = the former location of Holmia, 3 = Chenapou
(Aruataima) Falls.

Eigenmann, C. H. 1909. Reports on the Expedition to British Guiana of
the Indiana University and the Carnegie Museum, 1908. Report No. 1.
Some new genera and species of fishes from British Guiana. Ann. Carnegie
Mus. 6:4-54.

Eigenmann, C. H.1912. The freshwater fishes of British Guiana, including
a study of the ecological grouping of species and the relation of the fauna
of the plateau to that of the lowlands. Mem. Carnegie Mus. 5:1-578.